Date: Sun, 28 Nov 2010 13:24:54 +0300 From: Maxim Dounin <mdounin@mdounin.ru> To: Lawrence Stewart <lstewart@freebsd.org> Cc: Kostik Belousov <kostikbel@gmail.com>, freebsd-net@freebsd.org, Igor Sysoev <is@rambler-co.ru>, Andre Oppermann <andre@freebsd.org> Subject: Re: net.inet.tcp.slowstart_flightsize in 8-STABLE Message-ID: <20101128102453.GH72777@mdounin.ru> In-Reply-To: <4CF07771.7050409@freebsd.org> References: <20100927081217.GM44164@mdounin.ru> <4CA09987.8020205@freebsd.org> <20101102001134.GP44164@mdounin.ru> <4CD090EF.4020402@freebsd.org> <4CD64814.2000906@freebsd.org> <4CDD0C7D.1070102@freebsd.org> <4CDD1529.8070504@freebsd.org> <20101112104109.GY2392@deviant.kiev.zoral.com.ua> <4CDD3EA5.7020101@freebsd.org> <4CF07771.7050409@freebsd.org>
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Hello! On Sat, Nov 27, 2010 at 02:13:53PM +1100, Lawrence Stewart wrote: > On 11/13/10 00:18, Lawrence Stewart wrote: > > On 11/12/10 21:41, Kostik Belousov wrote: > >> On Fri, Nov 12, 2010 at 09:21:29PM +1100, Lawrence Stewart wrote: > >>> On 11/12/10 20:44, Lawrence Stewart wrote: > >>>> On 11/07/10 17:32, Lawrence Stewart wrote: > >>>>> On 11/03/10 09:30, Andre Oppermann wrote: > >>>>>> On 02.11.2010 01:11, Maxim Dounin wrote: > >>>>>>> Hello! > >>>>>>> > >>>>>>> On Mon, Sep 27, 2010 at 03:17:59PM +0200, Andre Oppermann wrote: > >>>>>>> > >>>>>>>> On 27.09.2010 10:12, Maxim Dounin wrote: > >>>>>>>>> Hello! > >>>>>>>>> > >>>>>>>>> On Mon, Sep 13, 2010 at 09:24:53PM +0400, Maxim Dounin wrote: > >>>>>>>>> > >>>>>>>>> [...] > >>>>>>>>> > >>>>>>>>>> Andre, could you please take a look at one more patch as well? > >>>>>>>>>> > >>>>>>>>>> Igor reported that it still sees 100ms delays with rfc3465 turned > >>>>>>>>>> on, and it turns out to be similar issue (setting cwnd to 1*MSS) > >>>>>>>>>> for hosts found in hostcache. > >>>>>>>>>> > >>>>>>>>>> The problem with setting cwnd from hostcache was already reported > >>>>>>>>>> here: > >>>>>>>>>> > >>>>>>>>>> http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/92690 > >>>>>>>>>> http://lists.freebsd.org/pipermail/freebsd-net/2007-July/014780.html > >>>>>>>>>> > >>>>>>>>>> As using larger cwnd from hostcache may cause problems on > >>>>>>>>>> congested links (see second thread) I changed code to only use > >>>>>>>>>> cached cwnd as an upper bound for cwnd (instead of fixing current > >>>>>>>>>> code). This is also in-line with what we do on connection > >>>>>>>>>> restarts. > >>>>>>>>>> > >>>>>>>>>> We may later consider re-adding usage of larger cwnd from > >>>>>>>>>> hostcache. But I believe it should be done carefully and > >>>>>>>>>> probably behind sysctl, off by default. > >>>>>>>>> > >>>>>>>>> Ping. > >>>>>>>> > >>>>>>>> Thanks for the reminder. I'll disable priming CWND from hostcache. > >>>>>>> > >>>>>>> Ping again. > >>>>>>> > >>>>>>> I would like to see the patch in question[1] committed and MFC'ed > >>>>>>> somewhere before 8.2. > >>>>>>> > >>>>>>> Andre, if you are just too busy to do it yourself - please say so, > >>>>>>> I'll ask somebody else to commit it. > >>>>>> > >>>>>> Thanks for the reminder. After EuroBSDCon Developer Summit I was > >>>>>> busy with other work and most of my tcp work was stalled due to > >>>>>> review bandwidth issues. > >>>>> > >>>>> Sorry for the review bandwidth issues. I'm only just managing to keep my > >>>>> head above water at the moment and have had to reduce much of my FreeBSD > >>>>> work to a trickle. > >>>>> > >>>>>> Lawrence, could you please spare a few seconds and take a quick look > >>>>>> at the attached patch? > >>>>> > >>>>> The patch looks fine, please commit. I hope to give the hostcache some > >>>>> TLC at some point, but in the meantime it's fine to ignore cached cwnd. > >>>> > >>>> FYI Andre, this patch got rolled into r215166 because I had to move all > >>>> the code around which the patch was based on. Is that going to cause any > >>>> issues here? I should have checked prior to committing but completely > >>>> forgot I had pulled the patch into my dev tree before creating the mod > >>>> CC patch. > >>> > >>> Gah, I think I've answered my own question. MFCing the patch standalone > >>> in time for 8.2 as Maxim requested is not going to be possible. I think > >>> I'll have to back out r215166, commit your patch and then recommit the > >>> modular CC patch. > >>> > >>> Unless someone can think of a way that doesn't involve all the mucking > >>> about? > >> Well, if the change is indeed already in HEAD, you can do a direct commit > >> to stable/8 after proper MFC period, noting that this is a cherry-pick of > >> the part of corresponding revision. > > > > hmm, not ideal but would get the job done. When I eventually MFC the > > modular CC patch everything will be back in sync mergeinfo wise as well. > > Would anyone object if I follow Kostik's suggestion and direct commit > > the TCP_METRICS_CWND patch to stable/8 in, say, a week's time? If I > > don't hear anything, I'll aim to do the commit next weekend. > > FYI, committed to stable/8 as r215925 and stable/7 as r215926. Thanks a lot. PR kern/92690 probably should be closed. Maxim Dounin
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